Paper compositions, imaging methods and methods for manufacturing paper

ABSTRACT

There is described a paper composition which comprises an anionic polymeric material and a binder material. The paper compositions of the invention are particularly useful as receiver materials for images formed by electrophotographic imaging methods utilizing liquid developers. Also described are imaging methods which utilize the paper compositions of the invention as receiver materials and methods for manufacturing the paper.

REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of prior, co-pendingprovisional application serial No. 60/412,132, filed Sep. 19, 2002.

FIELD OF THE INVENTION

[0002] This application relates to a novel paper composition and, moreparticularly, to paper which is suitable for use in electrophotographiccopying and printing methods using dry or liquid toners as well as tomethods for forming images on the paper and a method for manufacturingthe paper.

BACKGROUND OF THE INVENTION

[0003] In the well known art of electrophotography a latentelectrostatic image is initially formed on a photoconductive surface,typically by depositing a substantially uniform electrostatic charge onthe photoconductive surface and exposing the charged surface to animagewise pattern of radiation which corresponds to an image to bereproduced thereby discharging the photoconductive surface in animagewise pattern. The latent electrostatic image is then developed byapplying to it a composition of charged colored particles, which,depending upon the charge on the colored particles, that is, negative orpositive, can be arranged to adhere to areas of the photoconductivesurface having the higher potential or lower potential, respectively.The image thus formed on the photoconductive surface can then betransferred to a receiver material, typically paper, and adhered theretoso as to provide the desired reproduction. The development of the latentelectrostatic image can be either by a “dry” process wherein a drycomposition of colored particles is used or by a “wet” process whereincolored particles are dispersed in a liquid vehicle, typically aninsulating, nonpolar liquid such as mineral oil or the like.

[0004] The developer composition, which is utilized to form the visibleimage, includes particles of the image-forming material, commonlyreferred to as “toner”, such as, for example, carbon black, or othercolored pigments, or dyes, and a thermoplastic polymeric bindermaterial. The thermoplastic polymeric binder materials together withother charge control agents and the colored pigments, also referred tohereinafter as pigmented polymer particles, are chosen so as to impartthe desired charge triboelectrically to the image-forming material, aswell as to provide an adequate degree of plasticity either at thetemperature of the transferring surface or, where a specific fusing stepis used to bind the image to the receiver surface, at the temperaturesof the fusing step. The plasticity is necessary to fuse the pigmentedtoner particles together (cohesive strength), and to the paper (adhesivestrength).

[0005] As mentioned previously, the visible image formed on thephotoconductive surface is transferred to the receiver material. Suchtransfer can be made directly to a receiver material to form the finalhard copy image. There are also known electrophotographic imagingmethods in which the image formed on a photoconductive surface is firsttransferred to an intermediate transfer surface, also referred tohereinafter as ITS, and transferred from that surface to a finalreceiver material. Methods of this type are commonly referred to as“digital offset printing”. A method of this type, using a modulatedlaser beam to write the image on the photoconductor is described in U.S.Pat. No. 4,708,460.

[0006] According to the method described in U.S. Pat. No. 4,708,460, aphotoconductive drum is charged electrostatically, exposed imagewise bymeans of a laser, and the resulting latent image developed by applyingpigmented polymer particles in a liquid suspension, or emulsion, to thedrum. The image formed on the drum is transferred to an ITS, whereuponthe liquid vehicle, typically mineral oil or the like, is heated and asignificant amount is driven off and the pigmented polymer particles arecaused to melt or soften. Subsequently the image is transferred to afinal receiver sheet and adhered thereto. In monochrome printing asingle color image is formed on the receiver material. In multicolorprinting two or more separate monochrome images are formed on the drumin registration and transferred to the receiver sheet.

[0007] The receiver materials, which are useful in electrophotographiccopying and printing, including digital offset printing, are required tohave a number of characteristics. The receiver must be able to rapidlybond-the pigmented polymer particles in the short contact time betweenthe receiver and the transferring surface, or during the short durationof a receiver image fusing step. Hereinafter, any reference to dwelltime refers to the duration of either the image transfer step or thefusing step. The rapid bonding will result in strong adhesion of theimage-forming material to the receiver surface, which in turn willprovide maximum retention of the pigmented polymer particles on thereceiver surface, thereby resulting in high color saturation and imagecontrast. Also, where the printed image is strongly adhered to thereceiver surface, the image is afforded more protection from scratching,scuffing, or marring during subsequent handling and processing.

[0008] With strong image adhesion to the receiver surface during thetransfer step, complete or substantially complete transfer of thepigmented polymer particles can take place without leaving anyappreciable image residue on the transferring surface. In instanceswhere there is incomplete transfer of the image to the receiver surface,and repeated printing of the same image is carried out, a significantresidual image can be built up on the transferring surface, which cancause a ghost or spurious image to be seen when a different image isthen formed on the transferring surface and subsequently transferred tothe receiver. Additionally, for electrophotographic printing and copyingusing a liquid developer composition, the paper must be able to acceptthe liquid carrier for the pigmented polymer particles so as to not onlycreate good adhesive strength but also create good cohesive strength.

[0009] Receiver materials should also have a high surface strength so asto prevent unprinted area ghosting, or spurious images appearing on thereceiver surface. When the surface strength of the receiver is notsufficiently strong at the temperatures and pressures of the transferstep, material can transfer from the receiver to the transferringsurface, and with repeated printing of the same image, a significantdeposit can be built up on the transfer surface in non imaged areas.This build up can then create ghost or spurious images upon subsequentprinting of a different image. When paper is used as a receiver, andgiven the presence of fillers (clay, calcium carbonate, titanium dioxideetc), and fibers, typically used in papermaking, when such fillers andfibers are inadequately adhered to the surface, a deposit of suchmaterials can build up on the transferring surface, particularly whenhigher temperatures and pressures are used during image transfer, and asdescribed above, cause ghost or spurious images.

[0010] As the state of the art advances, there is a continuing need fornew and improved materials for use as final receiver materials in suchimaging methods.

SUMMARY OF THE INVENTION

[0011] It is therefore an object of this invention to provide a novelpaper composition.

[0012] It is another object of the invention to provide a papercomposition that is useful as a receiver material for images formed byimaging methods.

[0013] It is another object of the invention to provide a papercomposition which is useful as a receiver material for images formed byelectrophotographic imaging methods, including dry and wet copying andprinting methods.

[0014] Still another object of the invention is to provide a papercomposition which is useful as a receiver material for images formed byelectrophotographic imaging methods wherein the image is formed by aliquid developer composition, and the image is either transferred to areceiver and fused thereto or transferred to an intermediate transfersurface prior to being transferred to the receiver.

[0015] A further object is to provide an imaging method wherein thepaper composition of the invention is utilized as the receiver material.

[0016] Yet another object is to provide electrophotographic printingmethods including digital offset printing methods wherein a papercomposition according to the invention is utilized as the receivermaterial.

[0017] Still another object of the invention is to provide a method formanufacturing the paper of the invention.

[0018] In one aspect of the invention there is provided a papercomposition, which may be bleached, which comprises at least one anionicpolymeric material and at least one binder material and which does notinclude more than about 20% by weight of mechanical fiber; andpreferably not more than about 10%. In a preferred embodiment the paperincludes from about 0.1 to about 18.0 lbs/3300 ft² of finished paper ofat least one anionic polymeric material and from about 0.25 to about10.0 lbs/3300 ft² of finished paper of at least one binder material andparticularly preferably, from about 0.20 to about 5.0 lbs/3300 ft² offinished paper of at least one anionic polymeric material and from about1.0 to about 5.0 lbs/3300 ft² of finished paper of at least one bindermaterial.

[0019] As is known by those skilled in the art, “mechanical fiber”refers to groundwood pulp and thermomechanical pulp. Groundwood pulp isdefined as a mechanical wood pulp produced by pressing a barked logagainst a pulpstone and reducing the wood to a mass of relatively shortfibers. Thermomechanical pulp is defined as a high-yield pulp producedby a thermomechanical process in which wood particles are softened bypre-heating under pressure prior to a pressurized primary refiningstage. This type of pulp replaces or reduces the chemical pulp componentin newsprint or groundwood papers. See The Dictionary Of Paper, FourthEd., American Paper Institute, Inc., New York, N.Y. 1980, pages 205 and416.

[0020] The paper composition of the invention may be of any type,including paper typically used in dry and wet electrophotographiccopying and printing methods, paperboard, or poster board, and packagingpaper upon which images may be formed by various image-formingtechniques.

[0021] In another aspect of the invention there are provided imagingmethods including electrophotographic imaging methods, including dry andwet methods, and including both direct and indirect methods (offset) ofimage transfer, which utilize, as the receiver for the images formed,paper comprising at least one anionic polymeric material and at leastone binder material

[0022] According to another aspect of the invention there is provided amethod for manufacturing paper of the invention which comprises addingthe anionic polymeric material and the binder material, individually orin combination, at any point during the paper manufacturing method or atany point up to the formation of an image on the paper.

[0023] The anionic polymeric materials utilized according to theinvention contain repeat functional units capable of forming anionicsalts such as, for example, various polymeric carboxylic acids, sulfonicacids and phosphonic acids, which on reacting with bases can form thecorresponding salts. The anionic polymeric materials can be eitherhomopolymers or copolymers. The copolymers may be of any type includinggraft and block copolymers.

[0024] Any suitable binder materials may be utilized according to theinvention including for example, starches such as non-ionic starches,latexes, proteins, alginates, vegetable gums and cellulose derivativessuch as, for example, carboxymethylcellulose, hydroxymethylcellulose andthe like.

[0025] The anionic polymeric and binder materials can be applied to oneor both sides of the paper and can be applied either in the form ofsolutions, emulsions or dispersions of the polymers or copolymers or ascombinations thereof. Hereinafter, when reference is made to a polymer“mixture”, it should be understood that any such form is included. Theanionic polymeric materials and the binder materials may be applied incombination or separately.

[0026] Typical suitable anionic polymeric materials which are useful inaccordance with the invention include, for example, homopolymers ofacrylic acid, methacrylic acid, maleic acid, phosphonic acid, sulfonicacid and copolymers thereof with monomers such as ethylene, styrene,acrylamide, and acrylonitrile, including anionic polyacrylamide, thatis, polyacrylamide containing carboxylic acid functionality from eitheracrylic acid or methacrylic acid. Further, copolymers of maleicanhydride with ethylene or styrene can also be used.

[0027] Salts of the homopolymeric and copolymeric anionic materials mayalso be used including monovalent and polyvalent salts. Typical suitablemonovalent salts include ammonium salts and salts of alkali metals suchas sodium salts. Typical suitable polyvalent salts include salts ofmetals such as zinc and aluminum. If the anionic polymeric material isto be added during the papermaking process, then selection of the metalcation should be made to avoid undesirable interactions with other papermaking materials. Further, the anionic polymeric materials may be atleast partially esterified, that is, some or all of the repeatingfunctional units can be ester groups.

[0028] It has been found that the effectiveness of the paper in stronglyadhering the pigmented polymer particles to the paper surface is afunction of a number of factors including the plasticity, or mobility,of the anionic polymeric material, that is, its ability to rapidly comein contact with the pigmented polymeric toner particles at the receivertemperature during image transfer or fusing. The plasticity, ormobility, of the anionic polymeric material is a function of thesoftening temperature of the material. This property of the anionicpolymeric materials will be discussed in relation to their Vicatsoftening temperature. (See ASTM Test D1525-00 Standard Test Method ForVicat Softening Temperature of Plastics). Preferably, the Vicatsoftening temperature of the anionic polymeric material should be lessthan the receiver surface temperature during image transfer or fusingstep. Further, the shorter the dwell time of the image transfer orfusing step, it is preferred that the Vicat softening temperature shouldbe lower than the receiver surface temperature by a greater extent. In aparticularly preferred embodiment, the anionic polymeric material shouldhave a Vicat softening temperature of from about 10° C. to about 100° C.below the receiver surface temperature for dwell times in the range of1500 to 250 milliseconds.

[0029] As will be described later, for a preferred embodiment, thereceiver surface temperature, when in contact with an intermediatetransfer surface at a temperature in the vicinity of 125° C. (low end ofITS surface temperature range) for dwell times of 1000 milliseconds, maybe in the vicinity of about 90° C. For such a preferred embodiment,Vicat softening temperatures equal to, or less than about 90° C. arepreferred. The receiver surface temperature during an image fusing step,which can be practiced in dry or wet electrophotographic methods, andwhich is generally present in dry electrophotographic methods, can behigher. Fusing temperatures deployed typically range from about 100° C.to about 250° C. In these embodiments of the image-forming methods ofthe invention, the Vicat softening temperature of the anionic polymericmaterial could be up to about 180° C.

[0030] The Vicat softening temperature of the anionic polymericmaterials is dependent upon a number of factors. Such factors includethe type of anionic polymeric material, i.e., whether a homopolymer or acopolymer, and the particular chemical type of the repeat functionalunits. For example, homopolymers of polyacrylic acids or polymethacrylicacids typically have lower Vicat softening temperatures thanstyrenesulfonic acids. Polymaleic acids, being dicarboxyliic acids,typically have a much higher softening point than either polyacrylicacid or polymethacrylic acid. The copolymer type and ratio alsotypically have a significant effect on Vicat softening temperatures.Copolymers with ethylene or styrene typically have higher Vicatsoftening temperatures than the comparable anionic homopolymers. Ingeneral, the salts of these acids typically have higher Vicat softeningtemperatures compared to the acid form. Generally, the higher the degreeof salt formation, the higher will be the Vicat softening temperature.

[0031] Image adhesion is also a strong function of the retention of theanionic polymer at or near the paper surface, which is dependent, inpart, on the viscosity of the anionic polymer mixture and the method bywhich it is applied to the paper. In general, the higher the viscosity,with the upper limit being dependent on the application method selected,the lower will be the penetration of the anionic polymer into the paper,and the higher the concentration of the anionic polymer at or near thepaper surface. Other factors which influence the viscosity of themixture and hence the retention of the anionic polymer material at ornear the paper surface include the molecular weight of the polymer, thedegree of salt formation, the type of counter ion, and the pH of themixture.

[0032] Generally, the anionic polymer material should be compatible withthe pigmented polymer materials so as to ensure rapid bonding. For thecase of liquid developer electrophotography, the anionic polymericmaterial should also be compatible with the pigmented polymer carrierfluid, so as to ensure absorption of the carrier fluid into the paperfor both good cohesive and adhesive strength of the image.

[0033] The paper of the invention provides very good surface adhesion topigmented polymer particles thus providing complete or at leastsubstantially complete transfer of pigmented polymer particles used toform images in various electrophotographic imaging methods. Substantialtransfer of the pigmented polymer particles to the paper surfacesignificantly reduces or essentially eliminates any “ghost” images thatcan result from any image residue remaining on the transfer surface. Thepaper also rapidly absorbs liquids, typically used as the vehicle forliquid developers, such as, for example, insulating non-polar fluidssuch as aliphatic hydrocarbons used in certain electrophotographicimaging methods, to provide good cohesive strength of the receiverimage.

[0034] The paper of the invention also has a hard surface with stronglyadhered filler materials and paper fibers which is particularlyadvantageous in a preferred digital offset printing method of theinvention for the conditions of the image transfer from the intermediatetransfer surface to the paper as will be described in detail belowherein. The hard surface of the printing paper significantly reduces orsubstantially eliminates any intermediate transfer surface memory, orghosting, which can result in undesired “ghost” or spurious images onthe receiver from material transferred to the transfer surface in nonimage areas.

BRIEF DESCRIPTION OF THE DRAWING

[0035] For a better understanding of the invention as well as otherobjects and advantages and further features thereof, reference is madeto the following detailed description of various preferred embodimentsthereof taken in conjunction with the accompanying drawing wherein:

[0036]FIG. 1 is a diagram showing the paper path in one particularcommercial printing machine, the HP/Indigo 1000 TurboStream digitaloffset printing machine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] The paper composition of the invention may be of any typeincluding paperboard, or poster board, packaging paper and paperstypically used in copying and printing methods and comprises at leastone anionic polymeric material and at least one binder material and doesnot include more than about 20% by weight mechanical fiber andpreferably not more than 10% by weight. In a preferred embodiment thepaper includes from about 0.1 to about 18.0 lbs/3300 ft² of finishedpaper of at least one anionic polymeric material and from about 0.25 toabout 10.0 lbs/3300ft² of at least one binder material and particularlypreferably from about 0.2 to about 5.0 lbs/3300 ft² of finished paper ofat least one anionic polymeric material and from about 1.0 to about 5.0lbs/3300 ft² of finished paper of at least one binder material. Thepaper may have any basis weight. Preferably, the basis weight suitablefor paper used as the receiver in electrophotographic copying andprinting is in the range of from about 20 to about 400 pounds based on500 sheets of 25″ by 38″. Further, the paper composition may have anydesired gurly stiffness, measured according to standard TAPPIspecification T-543 (Bending Resistance of Paper). In a preferredembodiment the paper has gurly stiffness in the machine direction ofabout 25 to about 6000 grams.

[0038] As discussed previously, the anionic polymeric materials includerepeating units, which are capable of forming anionic salts. The anionicpolymer-may be a homopolymer or a copolymer. The homopolymer orcopolymer can be either in the acid form, or partially, or wholly, inthe salt form. As stated earlier, the Vicat softening temperature of ananionic polymer is affected by the degree of salt formation, the type ofcounter ion present, the valence of the counter ion, the molecularweight, copolymer type, copolymer ratio, pH of the polymer mixture fromwhich the material is applied to the paper and the degree ofesterification of the repeating functional units of the polymer.

[0039] In a particularly preferred embodiment, the Vicat softeningtemperature is from about 10° C. to about 100° C. lower than thereceiver surface temperature for dwell times in the range of 1500 to 250milliseconds. It is also preferred to apply the anionic polymericmaterial to the paper from a polymer mixture, which has a viscositysufficiently high to ensure maximum retention of the anionic polymer ator near the surface of the paper.

[0040] Selection of a specific anionic polymer or polymers for aparticular paper composition and the optimum amount(s) can be carriedout by standard experimental test practices. The selection can begreatly simplified by the use of a test method which simulates theenvironment of either image transfer or image fusion to the receiver.While the use of such a method can be fairly general and cover a broadrange of electrophotographic methods, the specific ranges of thevariables will depend upon the specific electrophotographic method. Asuitable method for initially testing anionic polymeric materials willnow be described by way of an example directed to the digital offsetliquid electrophotographic methods carried out using suitableelectrophotographic printing machines. By way of example only and not asa limitation, we refer to one family of machines, the HP/Indigo (HewlettPackard) electrophotographic printing machine models 1000 through 4000,all of which employ an intermediate transfer surface (ITS). Thoseskilled in the art will understand that other such machines can be usedto practice the invention.

[0041] A specific test apparatus is a transfer press such as, forexample, an AW-3000 Transfer Press made by Airwave Inc., Cincinnati,Ohio. Similar devices made by other manufacturers are commerciallyavailable and may be used for this purpose. The press consists of aheated platen with a lever that can serve as the base for the ITSmaterial. Once the ITS material is affixed to the platen, it can be usedto apply pigmented polymer to the paper surface under heat and pressure.The temperature of the platen is regulated to approximately simulate thereceiver surface temperatures typically encountered in the HP/Indigodigital offset printing machines mentioned above. The HP/Indigo digitalprinting machines typically have ITS surface temperatures of from about125° C. to about 180° C., resulting in receiver surface temperatures ofabout 90° C. for the lower end of the ITS range. Although not mandatory,it is desirable to use an intermediate transfer surface material similarto the one which is used in the actual printing machine. For theHP/Indigo printing machines mentioned above, an identical ITS material,that is, HP/Indigo product designation MPS 2177-42 was selected.Further, the surface temperature of the ITS in the test apparatus wasset at 105° C. for a majority of the testing so as to achieve a papersurface temperature in the vicinity of 90° C. for 1000 millisecond dwelltime. As stated above, this temperature simulates the lower end of thetemperature range of the intermediate transfer surface in the HP/Indigomachines. The lower end of the range was selected so as to increase thesensitivity.

[0042] As stated earlier, the anionic polymer should be compatible withboth the pigmented polymer and the carrier fluid in which it isdispersed. Since the composition of the specific pigmented polymer tonerparticles used in any commercial electrophotographic printing or copyingmachine is typically not in the public domain, it is preferable to usethe pigmented polymer particles actually used in the machine ofinterest. Thus, the black pigmented polymer available from HP/Indigohaving the product designation MPS 2131-42 was used. The same test canbe repeated for other color pigmented polymers. Generally, for thispractice of liquid electrophotography, it has been found that when theanionic polymer is a good bonding agent for the chosen black pigmentedpolymer, it will also satisfactorily bond to the pigmented polymers ofother colors.

[0043] In operation, the black pigment was diluted with mineral oil,specifically that available from HP/Indigo with a product designationMPS 2017-43, the pigmented polymer dispersant, and applied to the ITS,which was affixed to the platen of the transfer press. In general, thehigher the coverage of the pigmented polymer on the ITS surface, thegreater is the test sensitivity. Consequently, the coverage of the blackpigmented particles to be applied to the ITS, was established byapplying enough pigmented polymer particles so as to achieve an imagedensity of about 1.40 or higher on the paper surface.

[0044] The transfer press platen was then brought in contact with thepaper receiver containing the anionic polymer being tested. It is alsoimportant that the dwell time of the test, that is, the duration forwhich the heated ITS with the applied black pigmented polymer is incontact with the paper, be similar to that present in the actualprinting machine; in this instance approximately in the range of 300 to1000 milliseconds. The tests described below have been carried out atdwell times of both 250 and 1000 milliseconds, which adequately span therange in actual practice.

[0045] The paper samples with the transferred black-pigmented polymerwere then tested for adhesion efficacy via either cellophane tape, thatis, Highland® Clear 6200, or Scotch Drafting Tape® Brand 230, availablecommercially from 3M Corporation. The tape was applied uniformly to theprinted surface and a 1 Kg weight roller was applied to the papersurface twice to get good tape adhesion to the pigmented polymer on thepaper surface. The tape was then pulled away from the printed surface.Subsequently, the test sample was scanned with an Expression 1600scanner (Epson. Corp.), and the scanned sample analyzed for thepercentage of the material removed by the tape.

[0046] In Table 1 the test sensitivity is shown as a function of thetype of tape used. It can be seen that the cellophane tape gives poorerresults and is therefore more discriminating.

[0047] In Table 2, the adhesion test data are presented as a function ofdwell time. The dwell time data comparisons clearly indicate that, withall other variables being the same, adhesion is poorer at 250milliseconds dwell time compared to 1000 milliseconds dwell time. It canbe further seen that at lower coverages there is a higher sensitivity todwell time. A majority of the testing was carried out at both the high(1000) and low (250) dwell times.

[0048] Table 3 shows the results obtained with commercially availabledigital offset printing papers. It can be seen that all of the papersthat were tested, exhibited very poor adhesion.

[0049] In Table 4 the adhesion data are presented as a function ofanionic polymer coverage. It is seen that at higher coverages theadhesion is stronger. Thus, for polyethyleneacrylic acid at a coverageof 0.34 lb/3300 ft², there is a loss of about 14% from the tape pull.When the coverage was increased to 1.42 lbs/3300 ft², the loss was about4%. Generally, adhesion is seen to have improved as the coverageincreased. In testing different anionic polymers, a majority of thecomparative evaluations were undertaken at lower anionic polymercoverages so as to increase selectivity.

[0050] Table 5 shows the adhesion data as a function of viscosity of thepolymer mixture from which the anionic polymer was applied to the paper.For the same applied coverage of approximately 1.46 lbs/3300 ft², it canbe seen that adhesion performance at the lower viscosity issignificantly poorer. At the lower viscosity the results indicate thatthere was much greater penetration of the anionic polymer into the paperwith correspondingly lower surface retention, and hence, pooreradhesion.

[0051] Table 6 shows adhesion data as a function of molecular weight forpolyacrylic acid and polystyrenesulfonic acid homopolymers. The adhesionresults obtained with the acidic form of polyacrylic acid show that asthe molecular weight, and hence the polymer mixture viscosity, isincreased from 5,000 to 50,000, the adhesion results improve from about32% to about 7%, that is, only about 7% of the image-forming particleswere removed from the paper which had the highest molecular weightanionic polymer. This was so even though the lowest molecular weightpolymer was present at a significantly higher amount of 1.48 lbs/3300ft² compared to 0.93 lb/ft² for the higher molecular weight polymer.Comparing the adhesion performance of the 10,000 molecular weightpolymer versus the 50,000 molecular weight polymer at a similar coverageof about 0.9 lb/3300 ft², it is seen that the adhesion performanceimproved from a loss of about 15% to about 7%.

[0052] The data for polystyrenesulfonic acid polymers, at molecularweights of 70,000 and 400,000 (in the salt form) show again that at thehigher molecular weight the adhesion results are better, about a 12%loss for the higher molecular weight polymer compared to anapproximately 20% loss for the lower molecular weight material, eventhough the coverage for the former was somewhat lower at 0.26 lb/3300ft² versus 0.34 lb/3300 ft².

[0053] Thus, it can be seen that higher molecular weight anionicpolymers, which can increase polymer mixture viscosity and minimizeanionic polymer penetration into the paper, thereby increasing surfaceretention, can provide significantly improved adhesion performance.

[0054] In Table 7, the adhesion data are presented as a function of thesalt or acid form of the anionic polymer at dwell times of 1000 and 250milliseconds The data for the 70,000 molecular weightpolystyrenesulfonic acid in the acidic form, at both dwell times, showundesirably low adhesion as indicated by the approximately 41% and 59%losses, respectively. These data would indicate that due to the lowviscosity of the acid form of the polymer there was lower surfaceretention of the polymer and consequently poorer adhesion. The Na saltform of the polymer, which increases polymer mixture viscosity, at bothdwell times exhibited significantly better adhesion performance as seenby the approximately 20% and 18% losses, respectively.

[0055] As stated above, to increase selectivity, testing was undertakenat relatively low coverages of the anionic polymers. Consequently, theadhesion performance of the polymers can be further improved byincreasing the coverage of the polymers.

[0056] It is important to note however that although an anionic polymerof specific molecular weight, degree of neutralization, anionic polymercation, such as Li⁺, Na⁺, K⁺, NR₄ ⁺, valency of the cation and polymermixture pH can be selected to create the requisite anionic polymermixture viscosity for maximizing retention at or near the surface, andachieve good adhesion performance, nevertheless the Vicat softeningtemperature of the anionic polymeric material is also a very importantfactor in the adhesion performance of the paper of the invention. Thus,as stated above, it is preferred that the Vicat softening temperature bebelow the paper surface temperature during the transfer or fusing step.At the dwell time of 1000 milliseconds, and with the ITS at 105° C., thepaper surface temperature during transfer of the image from the ITS isestimated to be about 90° C. Although, the Vicat softening temperatureof the 400,000 molecular weight polystyrene sulfonate, at about 80° C.(Table 6) is higher than that of the polyethyleneacrylic acid, at about40° C. (Table 4), it is nevertheless still below the estimated papersurface temperature of 90° C. and its adhesion performance is comparableto that of polyethyleneacrylic acid at approximately similar coverage(See Table 4). Thus, the data shown in Table 6 and Table 7 indicatethat, in accordance with the preferred embodiment of the invention wherethe Vicat softening temperature is about 10° C. or more below the papersurface temperature during the transfer or fusing steps, the viscosityof the polymer mixture will have a significant effect on adhesionperformance, and desirable results can be achieved by selecting asufficiently high viscosity mixture consistent with the specificapplication technique selected.

[0057] In Tables 8 and 9 adhesion data are presented for anionicpolymers having a broad range of Vicat softening temperatures at dwelltimes of 1000 and 250 milliseconds respectively. It can be seen from thedata in Table 8 that both polyethylene acrylic acid and polymethacrylicacid, which have Vicat softening temperatures of about 40° C. or below,which are considerably lower than the paper surface temperature of 90°C., have approximately the same tape pull loss of about 13% at the lowcoverage of about 0.34 lb/3300 ft² and 0.42 lb/3300 ft², respectively.However, for polymaleic acid, with a Vicat softening temperature ofabout 110° C. which exceeds the paper surface temperature of 90° C., theadhesion performance dropped to an approximately 25% loss even thoughthe coverage was higher at 0.6 lb/3300 ft². The results forpolyethylenemaleic anhydride, with an even higher Vicat softeningtemperature showed an even larger deterioration of the adhesionperformance, an approximately 47% loss at similar coverage. The data inTable 9, obtained at the lower dwell time of 250 milliseconds, show evenhigher degradation for the polymaleic acid and polyethylenemaleicanhydride.

[0058] It should be noted that both polymaleic acid andpolyethylenemaleic anhydride are in the acid form, and the data clearlyindicate that as the Vicat softening temperature exceeds that of thepaper surface temperature, the adhesion results degraded, and exhibitedhigher sensitivity to dwell times. It should be further noted that fortests with the polystyrenesulfonic acid and polystyrene sulfonate (saltform), based on the surface pH measurement of the paper surface, it wasdetermined that the anionic polymer was less than 25% in the salt formafter being applied to the paper. For such cases, the Vicat softeningtemperature would not be significantly different from that of the acidform, and consequently the stated Vicat softening temperature is that ofthe acid form. See, for example the data shown in Tables 6 and 7.

[0059] The invention will now be further described with respect to thetypes of bonding which can occur, it being understood that thisdiscussion is for the purpose of assisting those skilled in the art tobetter understand and practice the invention, and there is no intentionto be bound to any theoretical mechanism by which the advantageousresults provided in accordance with the invention can be obtained sincesuch results have been demonstrated by actual experimentation.

[0060] It is believed that hydrogen bonding can occur to effectivelybond the anionic polymer to both the paper materials such as fibers andbinders (starch, etc.) as well as to the pigmented polymer particles.Typically, paper has a preponderance of sites capable of hydrogenbonding. Where the pigmented polymer also contains an adequatepercentage of polymeric anionic material, then hydrogen, or hydrophilic,bonding mechanisms can prevail to not only bind the anionic material tocomponents in the paper but also to the pigmented polymer particles,which form the image transferred to the paper, and be effective inproviding good adhesion. However, where the pigmented polymer particlesinclude copolymers, which may be likely, and the copolymer includes ahydrophobic moiety such as ethylene or styrene, employing a copolymer asthe anionic polymer may be advantageous.

[0061] It can be seen from Table 10 that polyethyleneacrylic acid, acopolymer, and polyacrylic acid, a homopolymer, at coverages ofapproximately 0.95 lb/3300 ft² have comparable adhesion data. Similarly,polyethyleneacrylic acid a copolymer, and polymethacrylic acid, ahomopolymer, at coverages of approximately 0.38 lb/3300 ft², havecomparable adhesion data. Further, comparing the adhesion performance ofthe sample having polyethyleneacrylic acid with 20% acrylic acid withthat of the sample having polyethyleneacrylic acid with 10% acrylicacid, that is, with a lower carboxylic acid content polymer, it can beagain seen that the adhesion performances are comparable. These resultsindicate that for the liquid electrophotographic methods carried out inthe HP/Indigo digital offset printing machines either hydrophilic orhydrophobic bonding would be quite effective in providing good adhesion.

[0062] Where stronger bonds are desired to provide extremely high degreeof adhesion strength, use of salts of homopolymers or copolymers withmultivalent metal ions can be considered. Polyvalent metal ions have thepotential to cross link polymer molecules and hence create strongeradhesion. Table 11 shows the adhesion performance data obtained withpolyethyleneacrylic acid in the acid form and in the salt form withpolyvalent aluminum as the counter ion. It can be seen that the samplewith the aluminum salt form exhibited better adhesion performance.

[0063] Based on an analysis of the data presented in Table 4 throughTable 11, it can be seen that the above test procedure has identified anumber of suitable anionic polymeric materials for incorporation in thepaper of the invention to be used as the receiver for the liquidelectrophotographic methods carried out in the HP/Indigo digital offsetprinting machines. The preferred anionic polymeric materials forincorporation in paper for use with these printing machines are:polyacrylic acid having a molecular weight of about 50,000;polymethacrylic acid having a molecular weight of about 15,000;polystyrenesulfonate (Na Salt) having a molecular weight of about400,000; and polyethyleneacrylic acid at either the 10% or the 20%acrylic acid. Also, the data show that some of the lower molecularweight anionic polymers such as polyacrylic acid having a molecularweight of about 10,000 or polystyrenesulfonate (Na Salt) having amolecular weight of about 70,000 could be suitable depending upon theapplication technique, the composition of the polymeric mixture, thatis, the presence of other viscosity building species such as starch or,by increasing anionic polymer solubility and hence viscosity via anincrease in polymer mixture pH. Further, the data show that otheranionic polymers such as polymaleic acid could be suitable at highertransfer or fusing temperatures.

[0064] Since there is high dependence of paper surface temperature on anumber of operational factors such as, for example, the basis weight ofthe paper used, with the higher basis weight providing a greater heatsink and lower surface temperature, ITS surface temperature, dwell timeetc., for greater robustness in performance, that is, an ability toprovide the desired results over a broader range of operationalconditions, it would be desirable to select the anionic polymer Vicatsoftening temperature, which is lower than the paper surface temperatureby a larger amount, that is, which is more towards the higher end of thepreferred temperature difference range of from about 10° C. to about100° C. Hence, the particularly preferred anionic polymeric materialsfor incorporation in the paper receiver for these applications are thepolyacrylic acid having a molecular weight of about 50000,polyethyleneacrylic acid at either the 10% acrylic acid or the 20%acrylic acid levels and the polymethacrylic acid, (salt form).

[0065] As stated earlier, the anionic polymeric material should bondwith both the paper materials as well as the pigmented polymer particlesso that they are retained on the paper surface. The adhesion of theanionic polymer to the paper is primarily through hydrogen bonding and,as discussed earlier, bonding to the pigmented polymer particles canalso be primarily, or partially, through hydrogen bonding. Thus, theactivity of the anionic polymer to adhere to the paper and in some casesto the pigmented polymer particles is directly related to the degree ofthe anionic polymer in the acid form. The pH of the anionic polymermixture from which the polymer is applied to the paper can be used toregulate the amount of polymer in the active, or acid, form and that inthe inactive, or dissociated, form. Generally, the higher the pH, thegreater is the inactive form. This effect can be seen from the data inTable 12. For example, comparing polyethyleneacrylic acid applied frompolymer mixtures at pH 6.9 and 7.3, the adhesion results are seen todegrade from 4% to 8% at the higher pH for the dwell time of 1000milliseconds and from 9% to 18% at the shorter 250 milliseconds dwelltime. Hereinafter, any reference to the active form of the anionicpolymer implies the acidic form of the polymer.

[0066] It was stated earlier that the paper receiver material shouldalso have a high surface strength so as to prevent unprinted areaghosting, or spurious images appearing on the receiver surface. Aprimary-requirement of the binder material then is to strongly bindtypical paper additives such as calcium carbonate, clay, titaniumdioxide and short, medium and long fibers in order to provide a hardpaper surface, which is substantially free from loose particles andfibers. Additionally, it was also stated that the paper surface shouldpreferably remain hard at the temperatures and pressures encounteredduring image transfer so as to prevent unprinted area ghosting, orspurious images appearing on the paper surface. The binder materialshould have sufficient binding strength to the typical paper additivesso as to minimize or substantially eliminate abrasion and transfer ofsuch paper additives and fibers during image transfer. Thus, the bindermaterial should be substantially unaffected with respect to its bindingstrength with respect to paper fibers, fillers, etc. at the temperatureof the paper during transfer.

[0067] Additionally, for the case of liquid electrophotographic printingmethods, as in the preferred embodiment, the binder material also shouldbe compatible with the carrier fluid or dispersant for the pigmentedpolymer particles. Upon application of the carrier fluid containing thepigmented polymer particles, the fluid should wet the paper and drainfrom the surface.

[0068] The binder materials may be anionic, cationic or neutral. Typicalsuitable binder materials which are useful in accordance with theinvention are starches, such as non-ionic starches, latexes, proteins,alginates, vegetable gums, and cellulose derivatives such as, forexample, carboxymethylcellulose, hydroxyethylcellulose and the like. Thebinder materials may be present in the paper individually or incombination. As stated earlier, for a preferred embodiment, the bindermaterial is present in the paper in an amount of from about 0.25 toabout 10.0 lbs/3300 ft², and particularly preferably from about 1.0 lbsto about 5.0 lbs/3300 ft² of finished paper.

[0069] Cost and other considerations in paper making often dictate theselection of materials that may not provide optimum results with respectto the primary requirements of either the anionic polymeric materials orbinder materials. For example, some naturally occurring or modifiednaturally occurring materials such as starch are very inexpensive andtherefore can be advantageously used as binder materials according tothe invention because of cost considerations. However, some-of thesestarches and other materials may not create a sufficient surfacehardness and thereby may create a significant intermediate surfacememory or ghosting phenomenon. In a preferred embodiment, because ofcost considerations, Ko-Film 280 starch, available commercially fromHercules Corp., is the binder material. In such cases, it then becomesadvantageous to use materials that significantly enhance the fulfillmentof the primary requirement of either the anionic polymeric material orthe binder material or both. Although test results indicate that Ko-Film280 starch binder material does not optimally fulfill the paper surfacestrength requirements at the temperatures of image transfer, it has beenfound that the performance of this binder material can be enhancedthrough the use of other materials.

[0070] Also, many of the starches and other binder materials, and paperfibers have cationic sites, which can preferentially bind to the anionicpolymer so as to markedly reduce the amount of anionic polymer availableto bind the image-forming pigments. Hence, during manufacture of thepaper containing the anionic polymer material, and particularly wherethe anionic polymer material and the binder are introducedsimultaneously, as is the case in a preferred embodiment, the anionicpolymer material may interact with other components such as cationicgroups in starches, as is the case with Ko-Film 280 starch. The datashown in Table 13 illustrate this phenomenon. It should be noted thatthe higher the percentage of the inactive form of the anionic polymerthe lower the interaction with anionically reactive materials such asKo-Film 280 starch.

[0071] Where the anionic polymer material has a high activity, unlesshigh coverages of the anionic polymer material are used, the functionalanionic units of the anionic polymer can get partially or wholly tied upwith the other paper materials including binder, thereby reducing theefficacy of the anionic polymer material to provide the desired adhesionresults. It was shown earlier (see Table 11) that the activity of theanionic polymer can be controlled with pH, that is, the higher the pHthe more inactive the anionic polymer. Thus, a particularly preferredanionic polymer for use in conjunction with Ko-Film 280 starch binder isthe salt of polyethyleneacrylic acid with a fugitive ammonium counterion, commercially available from Michelman Corporation with productdesignation MP 4990R. The ammonium salt form of the anionic polymer,depending upon the degree of conversion, which can be determined by thepH of the anionic polymer mixture, can be significantly inactivated atpH 7 and above. It was also shown earlier that the pH of the polymericmixture could be adjusted upward to achieve a lower degree of activationby the addition of NH₄OH. The key advantage obtained by reducing theactivity of the anionic polymer mixture is that it can minimize thepercentage of the anionic polymer interacting with components in thepaper as it is being applied to the paper. This in turn will allow moreof the anionic polymer to be available to bind the toner particles tothe paper surface. The significant advantage of having a fugitivecounter ion is that it can be driven off as NH₃ from the paper duringdrying, and given adequate temperatures and residence time in the dryer,the paper can essentially be completely active as it comes out of thedryer. When using the NH₄ salt, the dependency on the dryer to drive offthe ammonia is illustrated in Table 12. With the other variables beingthe same, it can be seen that as the temperature of the drying isreduced, a lower amount of the polymer reverts back to the active formand hence the adhesion performance degrades. Of course, the dryingduration can also have a similar effect.

[0072] Previously reference was made to the use of materials that cansignificantly enhance the fulfillment of the primary requirement ofeither the anionic material or the binder material or both. Two or moreanionic polymeric materials may be used in combination, as can two ormore binder materials. The specific anionic polymeric material(s) andthe binder material(s) in any specific paper composition according tothe invention-should be selected with respect to each other. Theselection criteria for any combination of anionic polymeric material(s)and binder material(s) include the selection of materials which exhibitvery good properties for one of the requirements of the respectivematerials and which also can provide at least some benefit with respectto another requirement. For, example, experiments have shown that whenanionic polyacrylamide, which has carboxylic acid functionality,commercially available from Hercules Corp. under product designation M1343, is used in conjunction with the ammonium salt ofpolyethyleneacrylic acid and Ko-Film 280 starch, dramatically improvedsurface strength of the paper at the temperatures of image transfer canbe obtained and thereby substantially lessen the presence of ghosting orspurious image from build up in non imaged areas. Additionally, thestrongly anionic polyacrylamide, although useful in accordance with theinvention but not as efficacious as polyethyleneacrylic acid, can alsoimprove the efficacy of the primary anionic material, that is,polyethyleneacrylic acid. It is believed that the strongly anionicpolyacrylamide preferentially binds to the cationic sites of a bindermaterial such as Ko-Film 280 starch thereby preventing such cationicsites from binding to the primary anionic polymer and thereby increasingits efficacy while also providing the additional benefit ofsubstantially reducing ghosting by cross-linking to the binder material.Thus, the use of anionic polyacrylamide can provide the multiplefunctions of binding to the cationic sites of a binder material,cross-linking the binder material and binding to the image-formingmaterial.

[0073] The respective amounts of the anionic polymeric and the bindermaterials, which are utilized in any specific paper composition, aredetermined in part by the number of functional groups in the molecule inrelation to the overall size of the molecule. The amounts of the anionicpolymeric material and binder material in the paper composition are alsoa function of the surface finish of the paper. The optimum amounts ofanionic polymer(s) and binder material(s) in any specific paper designedto be used with any specific printing or copying machine can bedetermined by routine scoping experiments.

[0074] As discussed previously, for good image quality there must bemaximum toner particle transfer to the paper receiver material andmaximum toner particle retention by the paper surface. The smoothness ofthe paper surface has a significant impact on the adhesion of the tonerparticles to the paper surface. A rougher surface typically has betteradhesion to the toner particles. However, a rougher surface typically isalso more susceptible to “ghosting.

[0075] The Sheffield method, described in TAPPI Test T-538, OM-96, whichis listed in TAPPI Test Methods (1996-1997), is a commonly acceptedtechnique for measuring the surface smoothness of paper. The papersmoothness is inversely proportional to the Sheffield number, i.e., thehigher the Sheffield numbers the rougher the paper surface. Generally,the Sheffield smoothness of the paper of the invention is from about 20to about 400.

[0076] A preferred printing paper of the invention comprises from about0.20 to about 5.0 lbs. of an ammonium salt of polyethyleneacrylic acid,(Michelman product designation MP 49990R), about 0.10 to about 1.0 lb ofanionic polyacrylamide, (Hercules product designation M1343) and aboutfrom about 1.0 to about 5.0 lbs of Ko-Film 280 starch, each based on3300 ft² of finished paper.

[0077] The electrophotographic printing methods provided according tothe invention include those where the pigmented polymer toner particlesare applied to the latent electrostatic image in a dry or wetcomposition with direct or indirect (offset) image transfer to receiver,and wherein an image is formed on a paper receiver material thatincludes at least one anionic polymeric binder material and at least onebinder material. In a preferred embodiment the paper used in theseprinting methods does not have more than about 20% by weight ofmechanical fiber and particularly preferably not more than about 10% byweight. In another preferred embodiment the paper used in these printingmethods includes from about 0.1 to about 18.0 lbs/3300 ft² of finishedpaper of at least one anionic polymeric material and from about 0.25 toabout 10.0 lbs/3300 ft² of finished paper of at least one bindermaterial and particularly preferably from about 0.2 to about 5.0/3300ft² of anionic polymeric material and from about 1.0 to about 5.0lbs/3300 ft² of at least one binder material.

[0078] Preferred electrophotographic methods are those digital offsetprinting methods wherein an electrostatic latent image formed on aphotoconductive surface, typically by applying a substantially uniformelectrostatic charge to the photoconductive surface and irradiating thecharged surface with image-modulated laser beam(s), is rendered visiblewith a liquid toner composition, transferred to a heated intermediatetransfer surface and transferred from the latter to the final paperreceiver material. Digital offset printing methods are well known in theart and therefore extensive discussion of such methods is not requiredhere.

[0079] An imaging method of this type is described in U.S. Pat. No.4,708,460. There is described in the '460 patent an apparatus wherein animage initially formed on a photoconductive surface by development witha liquid developer composition is transferred to an intermediate memberpositioned closely to the photoconductive member. The image issubsequently simultaneously transferred and fused to a copy sheet. Theprinting paper of the invention is useful as the receiver sheetaccording to this method.

[0080] The paper of the invention may be used as the receiver for imagesformed by any suitable electrophotographic printing machine. FIG. 1shows one particular printing machine, the Indigo TurboStream 1000digital offset printing machine, having a developer drum that attractsexcess non-image ink while repelling image ink, a PIP drum, whichcarries the image, an ITM drum on which a transfer blank is located, andan impression drum that forms a printing nip with the ITM drum. Thereare other commercially available printing machines with the same ordifferent configurations, which carry out either digital offset printingor direct transfer printing

[0081] Electrophotographic printing apparatus and methods can be used toform monochromatic and polychromatic images. Polychromatic, ormulticolor, images can be formed by two general methods. In one suchmethod monochromatic color separation images, e.g., magenta, yellow andcyan, are formed successively and each is transferred, in registration,to the receiver. Digital offset printing machines that carry out thismethod include the HP/Indigo 1000 and 3000 printing machines in whicheach individual color separation image is formed, transferred to theintermediate transfer surface and then to the paper receiver inregistration. In another such method, each color separation image isformed, transferred to an intermediate transfer surface in registrationto form the multicolor image on the intermediate transfer surface andthe multicolor image is then transferred to the paper receiver. Digitaloffset printing machines, which carry out this method, include theHP/Indigo 2000 and 4000 printing machines. Where the printing paper ofthe invention is used as the receiver for multicolor images formedaccording to the latter method it is preferred to utilize higherconcentrations of the anionic polymeric materials and binders since thecontact time of the paper with the heated intermediate transfer surfaceis less than in the former method where the receiver is brought intocontact with the heated intermediate transfer surface more than onetime, e.g., three or four times.

[0082] The paper of the invention may be produced by any conventionalmethod that converts fiber slurry into paper, and may be bleached.Further, the anionic polymeric material and the binder material may beapplied to the paper of the invention, either individually or incombination, at any point during the paper manufacture or they can beapplied to the paper at any point after the paper manufacture processand before the formation of an image on the paper. The anionic polymericmaterial and the binder material may be mixed with the pulp fiberslurry, which is made into a paper sheet. The pulp fiber may be mainlycomposed of wood pulp and may contain additionally a fibrous materialsuch as a synthetic pulp, synthetic fiber, glass fiber or the like. Theanionic polymer and binder materials may be applied to paper by means ofan air knife coater, a roll coater, a Champlex coater, a gravure coater,etc to a plain paper sheet or a coated sheet. Further, a plain paper orcoated sheet may be immersed in a mixture of the materials, which may bea solution, dispersion, emulsion or combinations thereof, excess fluidremoved and the paper dried.

[0083] In a preferred embodiment, both the anionic polymer and thebinder are applied to the paper at a size press addition station duringmanufacture of the paper. Simultaneous addition of these materials at asize press addition station confers significant cost advantages.However, there may be other situations where it is advantageous to applythe anionic polymer and/or the binder to the paper other than at thesize press addition station, including addition at any point after thepaper manufacturing process and before the formation of the image on thepaper.

[0084] The rheology of the anionic polymer and binder mixture at thesize press addition station should be optimized for the chosenapplication method. That is, the viscosity of the anionic polymermixture, under the conditions of being applied to the paper, asdiscussed earlier, should be sufficiently high so as to maximizeretention of the anionic polymer and binder materials at or very nearthe paper surface. For a specific anionic polymer and binder, maximizingthe percent solids of the anionic polymer mixture can also favorablyimpact the viscosity. It should be further noted that raising the pH tokeep the activity of the anionic polymer low would also increase thesolubility of the salt, and hence increase the viscosity. However, asstated earlier, the maximum viscosity at the time of application to thepaper has to be kept below the allowable maximum for the chosenapplication method. Additionally, it is also important to keep thetemperature of the size solution low so that NH₃ is not prematurelydriven off. The temperature of the paper coming in to the size pressstation will have a large impact on the temperature of the size presspolymer mixture. The temperature of the paper at the size press additionstation can be maintained at a desired low level by having coolingcapability either for the size station polymer mixture, or the incomingpaper, or both. For a preferred embodiment, the pH of the polymericmixture is from about 6 to 8.

EXAMPLES

[0085] The invention will now be further described in detail withrespect to various preferred embodiments by way of examples, it beingunderstood that these are intended to be illustrative only and theinvention is not limited to the materials, processes, or compositionsrecited therein. The papers according to the invention, described below,were printed in The HP/ Indigo TurboStream 1000 digital offset printingmachine, available from HP/Indigo, N.V., SM Veldhoven, Netherlands. Allparts and percentages recited in the examples are by weight unlessotherwise stated. All coverages are shown in lbs/3300 ft² of finishedpaper unless otherwise stated.

Example I

[0086] This example illustrates the pigment adhesion results obtainedfrom a digital offset printing method utilizing a printing paperaccording to the invention having a paper surface finish of Sheffield140 and varying amounts of an anionic polymeric material, namely anammonium salt of polyethyleneacrylic acid, (Michelman MP 4990R) Thebinder material was Ko-Film 280 starch present at about 2.1 lbs. A blackpigment was used to form the images on the paper TABLE I Amount ofpolyethyleneacrylic acid Adhesion Of Black Pigment 0.45 65%   0.57 85.8%0.97 93.6%

[0087] The adhesion values were obtained by applying a piece of ScotchDrafting Tape® Brand 230 tape to the image areas of the copy sheetfifteen minutes after printing the paper, and then peeling the tape fromthe paper. The image-forming pigment, which adhered to the tape was thenmeasured using a scanner. The percent adhesion values shown in Table Iare the percentages of pigment remaining on the paper. It can be seenthat the adhesion of the image-forming pigment to the paper improved asthe amount of polyethyleneacrylic acid present in the paper increased.

Example II

[0088] This example illustrates the pigment adhesion results obtainedfrom a digital offset printing method utilizing a printing paperaccording to the invention having a paper surface finish of Sheffield140 and varying amounts of the same anionic polymeric material describedin Example I, in combination with a second anionic polymeric material,namely, anionic polyacrylamide, (Hercules product designation M1343)present in an amount of about 0.33 lb/3300 ft² of finished paper. Thebinder material was Ko-Film 280 starch present at about 2.75 lbs/3300ft² of finished paper. A cyan pigment was used to form the images on thepaper. TABLE II Amount of polyethyleneacrylic acid Adhesion Of CyanPigment 0.45 93.8% 0.50 98.3%

[0089] It can be seen from a comparison of the results shown in Tables Iand II that the presence of the anionic polyacrylamide in combinationwith the ammonium salt of polyethyleneacrylic acid provided improvedimage pigment adhesion to the paper receiver.

Example III

[0090] This example illustrates the “ghosting” results obtained from adigital offset printing method utilizing a printing paper according tothe invention having a paper surface finish of Sheffield 140. Theseverity of the ghosting phenomenon can be judged by the number ofcleaning sheets of paper required to remove from the ITS the items whichcause the ghost images on the printed paper. This example illustratesthe results obtained with varying amounts of binder material. The bindermaterial was Ko-Film 280 starch. The anionic polymeric materialcomprised a combination of the ammonium salt of polyethyleneacrylic aciddescribed in Example I, present in an amount of from about 0.45 to about0.50 lb/3300 ft² of finished paper and the anionic polyacrylamidedescribed in Example II, present in the amount of about 0.33 lb/3300 ft²of finished paper.

[0091] 2000 Image cycles, of successive images were printed, that is,successive transfers of 2000 images from the intermediate transfersurface to the paper receiver material. After each 2000 image cycle sixcleaning sheets were printed. The cleaning sheets were paper sheetsaccording to the invention, which were processed in the digital offsetprinting machine identified above. The cleaning sheets did not have animage printed on them but rather had a yellow pigment uniformlydistributed across their surfaces. The cleaning sheets were examined forthe presence of the ghost image or image from the previous cycle. Thenumber of cleaning sheets shown is that required to remove from theintermediate transfer surface the residual material retained thereonafter three 2000 image cycles, described above, that is, a cumulativetransfer of 6000 images from the intermediate transfer surface to thepaper receiver material. TABLE III Amount of Binder Material Number OfCleaning Sheets 2.28 16 2.45 8 2.79 2

[0092] It can be seen that the severity of the ghosting phenomenon, asevidenced by the number of cleaning sheets required to remove from theintermediate transfer surface the materials causing the ghosting,decreased significantly as the amount of binder material was increased.

[0093] Although the invention has been described with respect to variouspreferred embodiments, it is not intended to be limited thereto, butrather those skilled in the art will recognize that variations andmodifications may be made therein which are within the spirit of theinvention and the scope of the appended claims. TABLE 1 TEST SENSITIVITYAS A FUNCTION OF TAPE TYPE COATED POLYMERIC MOLECULAR PRODUCT VICATSOFTENING COMPOUND TYPE EIGHT MW ACID/SALT VENDOR DESIGNATIONTEMPERATURE ° C. Poly Ethylene 80/20 17,000 NH₄SALT MICHELMAN MP4990R40° C. Acrylic Acid ETHYLENE/ ACRYLIC ACID Poly Ethylene 80/20 17,000NH₄SALT MICHELMAN MP4990R 40° C. Acrylic Acid ETHYLENE/ ACRYLIC ACIDPoly 80/20 17,000 NH₄SALT MICHELMAN MP4990R 40° C. Ethylene ETHYLENE/Acrylic Acid ACRYLIC ACID Poly 80/20 17,000 NH₄SALT MICHELMAN MP4990R40° C. Ethylene ETHYLENE/ Acrylic Acid ACRYLIC ACID COATED COVG IN DWELLTIME MILLI- #/REAM ITS TEMP ° C. TAPE USED SECONDS % LOSS 1.04 105° C.CELLOPHANE 1000 5.63 TAPE HIGHLAND 6200 CLEAR 1.04 105° C. SCOTCH 10003.14 DRAFTING TAPE 1.04  90° C. CELLOPHANE 1000 1.90 TAPE HIGHLAND 6200CLEAR 1.04  90° C. SCOTCH 1000 0 DRAFTING TAPE

[0094] TABLE 2 TEST SENSITIVITY AS A FUNCTION OF DWELL TIME COATEDPOLYMERIC MOLECULAR PRODUCT COMPOUND TYPE EIGHT MW ACID/SALT VENDORDESIGNATION POLY ETHYLENE 80/20 17,000 NH₄SALT MICHELMAN MP4990R ACRYLICACID ETHYLENE/ ACRYLIC ACID POLY ETHYLENE 80/20 17,000 NH₄SALT MICHELMANMP4990R ACRYLIC ACID ETHYLENE/ ACRYLIC ACID POLY ETHYLENE 80/20 17,000NH₄SALT MICHELMAN MP4990R ACRYLIC ACID ETHYLENE/ ACRYLIC ACID POLYETHYLENE 80/20 17,000 NH₄SALT MICHELMAN MP4990R ACRYLIC ACID ETHYLENE/ACRYLIC ACID POLY STYRENE Homo Polymer 70,000 ACID POLY SULFONIC ACIDSCIENCES POLY STYRENE Homo Polymer 70,000 ACID POLY SULFONIC ACIDSCIENCES VICAT SOFTENING COATED COVG IN DWELL TIME MILLI- TEMPERATURE °C. #/REAM ITS TEMP ° C. TAPE USED SECONDS % LOSS 40° C. 0.98 105° C.CELLOPHANE 1,000 6.34 TAPE HIGHLAND 6200 CLEAR 40° C. 0.98 105° C.CELLOPHANE 250 9.09 TAPE HIGHLAND 6200 CLEAR 40° C. 0.34 105° C.CELLOPHANE 1,000 13.78 TAPE HIGHLAND 6200 CLEAR 40° C. 0.34 105° C.CELLOPHANE 250 19.66 TAPE HIGHLAND 6200 CLEAR ˜70° C. 0.38 105° C.CELLOPHANE 1,000 41.09 TAPE HIGHLAND 6200 CLEAR ˜70° C. 0.38 105° C.CELLOPHANE 250 59.44 TAPE HIGHLAND 6200 CLEAR

[0095] TABLE 3 COMMERCIALLY AVAILABLE PAPER PRODUCT ADHESION PERFORMANCECOATED DWELL TIME MILLI- COMPOUND ITMSTEMP ° C. TAPE USED SECONDS % LOSSEastern Opaque 105° C. CELLOPHANE 1000 29.35% TAPE HIGHLAND 6200 CLEARXerox Color 105° C. CELLOPHANE 1000 26.29% Xpressions TAPE HIGHLAND 6200CLEAR Hammermill Color 105° C. CELLOPHANE 250 28.81% Copy TAPE HIGHLAND6200 CLEAR Georgia Pacific 105° C. CELLOPHANE 250 55.86% Microprint TAPEHIGHLAND 6200 CLEAR Xerox Color 105° C. CELLOPHANE 250 29.46% XpressionsTAPE HIGHLAND 6200 CLEAR

[0096] TABLE 4 IMPACT OF ANIONIC POLYMER COVERAGE ON ADHESION COATEDPOLYMERIC MOLECULAR PRODUCT COMPOUND TYPE EIGHT MW ACID/SALT VENDORDESIGNATION Poly Ethylene 80/20 17,000 NH₄SALT MICHELMAN MP4990R AcrylicAcid ETHYLENE/ ACRYLIC ACID Poly Ethylene 80/20 17,000 NH₄SALT MICHELMANMP4990R Acrylic Acid ETHYLENE/ ACRYLIC ACID Poly Ethylene 80/20 17,000NH₄SALT MICHELMAN MP4990R Acrylic Acid ETHYLENE/ ACRYLIC ACID PolyEthylene 80/20 17,000 NH₄SALT MICHELMAN MP4990R Acrylic Acid ETHYLENE/ACRYLIC ACID Poly Ethylene 80/20 17,000 NH₄SALT MICHELMAN MP4990RAcrylic Acid ETHYLENE/ ACRYLIC ACID VICAT SOFTENING COATED COVG IN DWELLTIME MILLI- TEMPERATURE ° C. #/REAM ITS TEMP ° C. TAPE USED SECONDS %LOSS 40° C. 1.42 105° C. CELLOPHANE 1,000 4.11 TAPE HIGHLAND 6200 CLEAR40° C. 1.04 105° C. CELLOPHANE 1,000 5.63 TAPE HIGHLAND 6200 CLEAR 40°C. 0.98 105° C. CELLOPHANE 1,000 6.34 TAPE HIGHLAND 6200 CLEAR 40° C.0.72 105° C. CELLOPHANE 1,000 7.50 TAPE HIGHLAND 6200 CLEAR 40° C. 0.34105° C. CELLOPHANE 1,000 13.78 TAPE HIGHLAND 6200 CLEAR

[0097] TABLE 5 IMPACT OF ANIONIC POLYMER MIXTURE VISCOSITY ON ADHESIONSOLUTION/Dis- persion VilSCOSITY COATED POLYMERIC MOL WEIGHT CENTIPRODUCT COMPOUND TYPE M_(W) ACID/SALT POISE @2 VENDOR DESIGNATION PolyEthylene 80/20 17,000 NH₄ 447 MICHELMAN MP4990R Acrylic Acid ETHYLENE/SALT 35% ACRYLIC DISPERSION ACID 50% DILUTION 80/20 17,000 NH₄  8*MICHELMAN MP4990R ETHYLENE/ SALT ACRYLIC ACID VICAT SOFTENING COATEDCOVG IN DWELL TIME MILLI- TEMPERATURE ° C. #/REAM ITS TEMP ° C. TAPEUSED SECONDS % LOSS 40° C. 1.42 105° C. CELLOPHANE 1,000 4.11 TAPEHIGHLAND 6200 CLEAR 40° C. 1.51 105° C. CELLOPHANE 1,000 12.25 TAPEHIGHLAND 6200 CLEAR

[0098] TABLE 6 IMPACT OF ANIONIC POLYMER MOLECULAR WEIGHT ON ADHESIONCOATED POLYMERIC MOL WEIGHT PRODUCT COMPOUND TYPE M_(W) ACID/SALT VENDORDESIGNATION POLY ACRYLIC HOMO 5,000 Acid ALDRICH CAS # ACID POLYMER9003-01-4 POLY ACRYLIC HOMO 10,000 Acid ALDRICH CAS # ACID POLYMER9003-01-4 POLY ACRYLIC HOMO 50,000 Acid ALDRICH CAS # ACID POLYMER9003-01-4 POLY STYRENE HOMO 70,000 Acid POLY CAS # SULFONIC ACID POLYMERSCIENCES 28210-41-5 POLY STYRENE HOMO 70,000 Na POLY CAS # SULFONATEPOLYMER SALT SCIENCES 2695-37-6 POLY STYRENE HOMO 400,000 Na POLY CAS #SULFONATE POLYMER SALT SCIENCES 2695-37-6 TAPE USED CELLOPHANE VICATSOFTENING COATED COVG IN TAPE HIGHLAND DWELL TIME MILLI- TEMPERATURE °C. #/REAM ITS TEMP 6200 CLEAR SECONDS % LOSS <40° C. 1.48 105° C.CELLOPHANE 1000 31.75% TAPE <40° C. 0.9 105° C. CELLOPHANE 1000 14.91%TAPE <40° C. 0.93 105° C. CELLOPHANE 1000 6.50% TAPE ˜70° C. 0.38 105°C. CELLOPHANE 1000 41.09% TAPE ˜70° C.* 0.34 105° C. CELLOPHANE 100020.09% TAPE ˜80° C.* 0.26 105° C. CELLOPHANE 1000 12.31% TAPE

[0099] TABLE 7 IMPACT OF ACID & SALT FORM OF ANIONIC POLYMER ON ADHESIONCOATED POLYMERIC MOL WEIGHT PRODUCT COMPOUND TYPE M_(W) ACID/SALT VENDORDESIGNATION POLY STYRENE HOMO 70,000 SULFONIC POLY CAS # SULFONIC ACIDPOLYMER ACID SCIENCES 28210-41-5 POLY STYRENE HOMO 70,000 Na SALT POLYCAS # SULFONATE POLYMER SCIENCES 2695-37-6 POLY STYRENE HOMO 70,000SULFONIC POLY CAS # SULFONIC ACID POLYMER ACID SCIENCES 28210-41-5 POLYSTYRENE HOMO 70,000 Na SALT POLY CAS # SULFONATE POLYMER SCIENCES2695-37-6 TAPE USED CELLOPHANE VICAT SOFTENING COATED COVG IN TAPEHIGHLAND DWELL TIME MILLI- TEMPERATURE ° C. #/REAM ITS TEMP ° C. 6200CLEAR SECONDS % LOSS ˜70° C. 0.38 105° C. CELLOPHANE 1,000 41.09 TAPE˜70° C. 0.34 105° C. CELLOPHANE 1,000 20.09 TAPE ˜70° C. 0.38 105° C.CELLOPHANE 250 59.44 TAPE ˜70° C.* 0.34 105° C. CELLOPHANE 250 18.43TAPE

[0100] TABLE 8 IMPACT OF VICAT SOFTENING TEMPERATURES ON ADHESION COATEDPOLYMERIC MOL WEIGHT PRODUCT COMPOUND TYPE M_(W) ACID/SALT VENDORDESIGNATION Poly Ethylene 80/20 17,000 NH₄ MICHELMAN MP4990R AcrylicAcid ETHYLENE/ SALT ACRYLIC ACID Poly Methacrylic HOMO 15,000 Na POLYCAS # Acid POLYMER SALT SCIENCES 25087-26-7 POLY MALEIC HOMO 1,000 ACIDPOLY CAS # ACID POLYMER SCIENCES 26099-09-2 POLY ETHYLENE HOMO ACID POLYCAS # MALEIC POLYMER SCIENCES 9006-26-2 ANHYDRIDE TAPE USED CELLOPHANEVICAT SOFTENING COATED COVG IN TAPE HIGHLAND DWELL TIME MILLI-TEMPERATURE ° C. #/REAM ITS TEMP ° C. 6200 CLEAR SECONDS % LOSS 40° C.0.34 105° C. CELLOPHANE 1,000 13.78 TAPE <40° C. 0.42 105° C. CELLOPHANE1,000 13.25 TAPE ˜110° C. 0.6 105° C. CELLOPHANE 1,000 25.34 TAPE ˜120°C. 0.31 105° C. CELLOPHANE 1,000 47.28 TAPE

[0101] TABLE 9 IMPACT OF VICAT SOFTENING TEMPERATURES ON ADHESION COATEDPOLYMERIC MOL WEIGHT PRODUCT COMPOUND TYPE M_(W) ACID/SALT VENDORDESIGNATION Poly Ethylene 80/20 17,000 NH₄ MICHELMAN MP4990R AcrylicAcid ETHYLENE/ SALT ACRYLIC ACID Poly Methacrylic HOMO 15,000 Na POLYCAS # Acid POLYMER Salt SCIENCES 25087-26-7 POLY MALEIC HOMO 1500 ACIDPOLY CAS # ACID POLYMER SCIENCES 26099-09-2 POLY HOMO ACID POLY CAS #ETHYLENE POLYMER SCIENCES 9006-26-2 MALEIC ANHYDRIDE TAPE USEDCELLOPHANE VICAT SOFTENING COATED COVG IN TAPE HIGHLAND DWELL TIMEMILLI- TEMPERATURE ° C. #/REAM ITMSTEMP ° C. 6200 CLEAR SECONDS % LOSS40° C. 0.34 105° C. CELLOPHANE 250 19.66 TAPE <40° C. 0.42 105° C.CELLOPHANE 250 14.33 TAPE ˜110° C. 0.6 105° C. CELLOPHANE 250 31.76 TAPE˜140° C. 0.31 105° C. CELLOPHANE 250 57.00 TAPE

[0102] TABLE 10 HYDROPHILLIC AND HYDROPHOBIC BONDING IMPACT ON ADHESIONCOATED POLYMERIC MOL WEIGHT PRODUCT COMPOUND TYPE M_(W) ACID/SALT VENDORDESIGNATION Poly Ethylene 80/20 17,000 NH₄ MICHELMAN MP4990R AcrylicAcid ETHYLENE/ SALT ACRYLIC ACID POLY 0/100 50,000 ACID ALDRICH ACRYLICACID HOMOPOLYMER Poly 80/20 17,000 NH₄ MICHELMAN MP4990R EthyleneETHYLENE/ SALT Acrylic Acid ACRYLIC ACID POLY HOMO 15,000 Na ALDRICH CAS# Methacrylic POLYMER Salt 25087-26-7 ACID Poly 80/20   7000* NH₄MICHELMAN MP4990R Ethylene ETHYLENE/ SALT Acrylic Acid ACRYLIC ACID Poly90/10  13000* NH₄ MICHELMAN MP2960 Ethylene ETHYLENE/ SALT Acrylic AcidACRYLIC ACID VICAT SOFTENING COATED COVG IN DWELL TIME MILLI-TEMPERATURE ° C. #/REAM ITM TEMP ° C. SECONDS % LOSS 40° C. 0.98 105° C.1,000 6.34 <<40° C. 0.93 105° C. 1,000 6.50 40° C. 0.34 105° C. 1,00013.78 ˜50° C. 0.42 105° C. 1,000 14.33 40° C. 1.42 105° C. 1,000 4.1172° C. 1.53 105° C. 1,000 3.72

[0103] TABLE 11 IMPACT OFPOLYVALENT METAL ION ON ADHESION COATEDPOLYMERIC MOL WEIGHT PRODUCT COMPOUND TYPE M_(W) ACID/SALT VENDORDESIGNATION Poly Ethylene 80/20 17,000 NH₄ MICHELMAN MP4990R AcrylicAcid ETHYLENE/ SALT ACRYLIC ACID Poly Ethylene 80/20 17,000 NH₄ AcrylicAcid ETHYLENE/ SALT (Above) + ALUM ACRYLIC ACID Poly Ethylene 80/2017,000 NH₄ MICHELMAN MP4990R Acrylic Acid ETHYLENE/ SALT ACRYLIC ACIDPoly Ethylene 80/20 17,000 NH₄ Acrylic Acid ETHYLENE/ SALT (Above) +ALUM ACRYLIC ACID TAPE USED CELLOPHANE VICAT SOFTENING COATED COVG INTAPE HIGHLAND DWELL TIME MILLI- TEMPERATURE ° C. #/REAM ITS TEMP ° C.6200 CLEAR SECONDS % LOSS 40° C. 1.04 105° C. CELLOPHANE 1,000 5.03 TAPE1.04 + 0.3 105° C. CELLOPHANE 1,000 4.39 TAPE 40° C. 1.04 90° C.CELLOPHANE 1,000 1.90 TAPE 1.04 + 0.3 90° C. CELLOPHANE 1,000 0.30 TAPE

[0104] TABLE 12 IMPACT OFANIONIC POLYMER ACTIVITY ON ADHESION COATED MOLWEIGHT Anionic Polymer PRODUCT COMPOUND POLYMERIC TYPE M_(W) ACID/SALTMixture Ph VENDOR DESIGNATION Poly Ethylene 80/20 POLY 17,000 NH₄ 6.9MICHELMAN MP 4990R Acrylic Acid ETHYLENE/ACRYLIC SALT ACID Poly Ethylene80/20 17,000 NH₄ 6.9 MICHELMAN MP 4990R Acrylic Acid ETHYLENE/ACRYLICSALT ACID Poly Ethylene 80/20 17,000 NH₄ 6.9 MICHELMAN MP 4990R AcrylicAcid POLYETHYLENE/ SALT ACRYLIC ACID Poly Ethylene 80/20 17,000 NH₄ 6.9MICHELMAN MP4900R Acrylic Acid POLYETHYLENE/ SALT ACRYLIC ACID PolyEthylene 80/20 17,000 NH₄ 7.3 MICHELMAN MP4990R Acrylic AcidPOLYETHYLENE/ SALT (Above) + ACRYLIC ACID NH₄OH Poly Ethylene 80/2017,000 NH₄ 6.9 MICHELMAN MP 4990R Acrylic Acid POLYETHYLENE/ SALTACRYLIC ACID Poly Ethylene 80/20 17,000 NH₄ 7.3 MICHELMAN MP4990RAcrylic Acid POLYETHYLENE/ SALT (Above) + ACRYLIC ACID NH₄OH VICATSOFTENING COATED COVG IN DRYING DURATION DWELL TIME MILLI- TEMPERATURE °C. #/REAM DRYING TEMP MIN SECONDS % LOSS 40° C. 0.98 153° C. 2 1,0006.34 (305° F.) 40° C. 1.02 121° C. 2 1,000 8.43 (250° F.) 40° C. 0.88107° C. 2 1,000 14.94 (225° F.) 40° C. 1.42 153° C. 2 1,000 4.11 (305°F.) 40° C. 1.32 153° C. 2 1,000 8.00 (305° F.) 40° C. 0.98 153° C. 2 2509.09 (305° F.) 40° C. 1.01 153° C. 2 250 18.04 (305° F.)

[0105] TABLE 13 IMPACT OF STARCH ANIONIC POLYMER MIXTURES ON ADHESIONCOATED MOL WEIGHT PRODUCT VICAT SOFTENING COMPOUND POLYMERIC TYPE M_(W)ACID/SALT VENDOR DESIGNATION TEMPERATURE ° C. Poly Ethylene 80/20 17,000NH₄ MICHELMAN MP 4990R 40° C. Acrylic Acid POLYETHYLENE/ SALT ACRYLICACID Poly Ethylene 80/20 17,000 NH₄ MICHELMAN MP 4990R 40° C. AcrylicAcid ETHYLENE/ SALT ACRYLIC ACID ANIONIC POLYMER STARCH COVG IN COVG INLbs/3300 DRYING DURATION DWELL TIME MILLI- Lbs/3300 Sq Ft Sq Ft DRYINGTEMP MIN SECONDS % LOSS 0 0.34 153° C. 2 1,000 13.78 (305° F.) 2.99 0.48121° C. 2 1,000 24.15 (250° F.)

What is claimed is:
 1. A paper composition comprising at least one anionic polymeric material and at least one binder material and not having more than about 20% by weight of mechanical fiber.
 2. A paper composition as defined in claim 1 not having more than about 10% by weight of mechanical fiber.
 3. A paper composition as defined in claim 1 comprising from about 0.1 to about 18.0 lbs/3300 ft² of finished paper of at least one anionic polymeric material and from about 0.25 to about 10.0 lbs/3300 ft² of finished paper of at least one binder material
 4. A paper composition as defined in claim 1 comprising from about 0.20 to about 5.0 lbs/3300 ft² of finished paper of at least one anionic polymeric material and from about 1.0 to about 5.0 lbs/3300 ft² of finished paper of at least one binder material.
 5. A paper composition as defined in claim 1 wherein said anionic polymer material is selected from the group consisting of homopolymers, copolymers and mixtures thereof.
 6. A paper composition as defined in claim 1 wherein said anionic polymeric material is selected from the group consisting of polyacrylic acid, polymethacrylic acid, polyethyleneacrylic acid, polystyrene sulfonate, anionic polyacrylamide, polystyreneacrylic acid and mixtures thereof.
 7. A paper composition as defined in claim 1 wherein said anionic polymer is in the salt form.
 8. A paper composition as defined in claim 7 wherein said anionic polymeric material is an ammonium salt of polyethyleneacrylic acid.
 9. A paper composition as defined in claim 8 and further including anionic polyacrylamide
 10. A paper composition as defined in claim 1 wherein said binder material is selected from the group consisting of starch, latexes, proteins, alginates, vegetable gums and cellulose derivatives.
 11. A paper composition as defined in claim 10 wherein said binder comprises starch and said anionic polymeric material comprises anionic polyacrylamide and an ammonium salt of polyethyleneacrylic acid.
 12. A paper composition as defined in claim 11 comprising from about 0.20 to about 5.0 lbs of an ammonium salt of polyethyleneacrylic acid, from about 0.10 to about 1.0 lb of anionic polyacrylamide and from about 1.0 to about 5.0 lbs of starch, each based on 3300 ft² of finished paper.
 13. A paper composition as defined in claim 1 wherein said anionic polymeric material has a Vicat softening temperature which is equal to or less than about 90° C.
 14. An imaging method comprising the steps of: a. forming an image; and b. transferring said image to a sheet of paper comprising at least one anionic polymeric material and at least one binder material.
 15. The imaging method as defined in claim 14 wherein said paper does not have more than about 20% by weight of mechanical fiber.
 16. The imaging method as defined in claim 14 wherein said paper does not have more than about 10% by weight of mechanical fiber.
 17. The imaging method as defined in claim 14 wherein said paper comprises from about 0.1 to about 18.0 lbs/3300 ft² of finished paper of said anionic polymeric material and from about 0.25 to about 10.0 lbs/3300 ft² of finished paper of said binder material.
 18. The imaging method as defined in claim 14 wherein said paper comprises from about 0.2 to about 5.0 lbs/3300 ft² of finished paper of at least one anionic polymeric material and from about 1.0 to about 5.0 lbs/3300 ft² of finished paper of at least one binder material.
 19. The imaging method as defined in claim 14 wherein step a. comprises forming said image on a photoconductive surface utilizing a liquid developer composition and transferring said image from said photoconductive surface to a heated intermediate transfer surface and step b. comprises transferring said image from said intermediate transfer surface to said sheet of paper.
 20. The imaging method as defined in claim 19 wherein during step b. said intermediate surface has a temperature of from about 100° C. to about 200° C.
 21. The imaging method as defined in claim 20 wherein said anionic polymeric material has a softening temperature of from about 10° C. to about 100° C. less than the temperature of the surface of said paper when it is in contact with said intermediate transfer surface.
 22. The imaging method as defined in claim 21 wherein said anionic polymeric material has a softening temperature of about 40° C.
 23. The imaging method as defined in claim 21 wherein said paper composition comprises an ammonium salt of polyethyleneacrylic acid, anionic polyacrylamide and starch.
 24. The imaging method as defined in claim 23 wherein said paper composition comprises from about 0.20 to about 5.0 lbs of an ammonium salt of polyethyleneacrylic acid, from about 0.10 to about 1.0 lb of anionic polyacrylamide and about 1.0 to about 5.0 lbs of starch, each based on 3300 ft² of finished paper.
 25. The imaging method as defined in claim 14 wherein step a. comprises irradiating a substantially uniformly electrostatically charged photoconductive surface with an imagewise-modulated laser beam.
 26. The imaging method as defined in claim 14 wherein step a. comprises forming said image on a photoconductive surface and further including the step of fusing said image to said paper sheet.
 27. The imaging method as defined in claim 26 wherein said anionic polymeric material has a softening temperature equal or less than 180° C.
 28. A method for manufacturing paper comprising applying at least one anionic polymeric material and at lest one binder material to a paper composition to obtain a paper having not more than about 20% by weight of mechanical fiber.
 29. The method as defined in claim 28 wherein said paper composition does not have more than about 10% by weight of mechanical fiber.
 30. The method as defined in claim 28 wherein said anionic polymeric material and said binder material are applied from a solution, dispersion, emulsion or combinations thereof,
 31. The method as defined in claim 28 wherein said anionic polymeric material and said binder materials are applied at a size press addition station.
 32. The method as defined in claim 28 wherein said anionic polymeric material and said binder material are applied from a solution, dispersion, emulsion or combinations thereof having a pH of from about 6 to
 8. 